Chemiluminescent assay of lipid hydroperoxides quantification in emulsions of fatty acids and oils

Lipid hydroperoxides (LOOH) are relatively stable intermediates which arise during oxidation of fats and lipids. The luminol-enhanced chemiluminescent (LCL) method has been applied to detect the LOOH formed during thermal oxidation. The method was optimized for best signal to noise ratio what gave reliable and sensitive data up to 50 pM of detected hydroperoxides (approximately 1 μmol hydroperoxides/kg lipid). The observed LCL signal was calibrated with 13-HPODE (13-(S)-hydroperoxy-9Z,11E-octadecadienoic acid) as an external hydroperoxide standard. This allowed quantitative determination of LOOH formed during thermal oxidation of linoleic acid and phosphatidylcholine (PC) in emulsion and during storage of linseed oil. The obtained LCL results were validated using HPLC, spectrophotometric assay for conjugated dienes at 234 nm and iodometric titration peroxide value (PV) methods.The described LCL method is direct, sensitive, fast and simple, however, it is not specific to the lipids and may be used to determine the presence of the other types of hydroperoxides or the other oxidizing agents what finally gives overall total antioxidant estimation of the sample.